1. Field of the Invention
The present invention relates to a novel bacteriocin derived from a Lactococcus and method of use to inhibit bacteria, particularly in foods and other materials in need of protection from the bacteria. The present invention particularly relates to a bacteriocin produced by Lactococcus lactis LL-1 deposited as NRRL-B-18535 (previously known as Streptococcus lactis).
2. Prior Art
The lactic streptococci have been previously described to produce a variety of polypeptide antibiotics, diplococcin, lactostrepcins and bacteriocins (Klaenhammer, T. R., Biochemie 70: 337-349 (1988)). The term nisin describes a family of polypeptide antibiotics produced by Lactococcus lactis that prevents the outgrowth of Clostridium and Bacillus spores (Eapen, K. C., et al., J. Food. Sci. Technol. 20: 231-240 (1983)). Bacteriocins are also produced by pediococci.
Diplococcin is an antimicrobial agent produced by Lactococcus cremoris. This inhibitor does not inhibit sporeformers and is only active against other dairy lactococci (Davey, G. P. and B. C. Richardson., Appl. Environ. Microbiol. 41:84-89 (1981)).
Lactostrepcins are inhibitory proteins produced by the lactococci that inhibit other streptococci. These molecules are active at relatively low pH and activity is completely lost when the pH is raised to 7.0 (Kozak, W., et al., J. Dairy Res. 45: 247-257 (1978)).
Bacteriocins produced by lactic lactococci have been observed in many commercial strains (Geis, A., et al., Appl. Environ. Microbiol. 45:205-211 (1983)). Eight bacteriocin types (I-VIII) have been identified on the basis of their activity spectrum, proteolytic enzyme susceptibility, heat stability and cross-reaction with other bacteriocin producers (Geis, A., et al. Appl. Environ. Microbiol. 45:205-211 (1983)).
The problem is that the bacteriocins are not active over a wide pH range. It would be very desirable to provide a bacteriocin which is useful in a wide variety of foods regardless of whether they are acidic or basic.